This invention relates in general to electrically actuated latch assemblies and, in particular, to an improved structure for an electrically actuated vehicle door latch having a double locking antitheft feature.
Vehicles such as passenger cars are commonly equipped with individual latch assemblies which secure respective passenger and driver doors. Each latch assembly is typically provided with manual latch actuating mechanisms for unlatching the latch assembly from outside and inside the vehicle, e.g., respective outer and inner door handles. Each latch assembly is also typically provided with an individual mechanical lock which may be provided with a key operated locking mechanism for operating the lock from the exterior of the vehicle and provided with manual locking mechanism for operating inside the vehicle, e.g., a respective sill button. Further, these locks are commonly provided with a locking mechanism for remote operation, such as an electrically operated mechanism for actuating the lock.
As is commonly known, the lock may be actuated to prevent release of the latch assembly. On vehicles with an interior manual locking mechanism, a thief may break a window of the vehicle and reach inside to manually unlock the latch assembly. It has therefore been proposed to provide a latch assembly having a "double lock" feature by which the interior manual locking mechanism may be selectively disabled when the occupant exits the vehicle. A vehicle having latch assemblies thus equipped with a double lock feature would be a less attractive target for thieves.
Generally, such a double lock feature has been provided by blocking latch assembly components from moving from a locked position to an unlocked position when the latch assembly is double locked. As described in U.S. Pat. Nos. 4,342,209 to Kleefeldt and 4,669,283 to Ingehoven, the double lock position is set by an electric motor actuator having a motor whose output shaft is a spindle on which is threaded a nut that acts to block the inside lock element in the locked position. Thus the structure must be strong enough to withstand whatever force a would-be thief is willing to apply. Hence, the elements must be made fairly robust and, therefore, are expensive to manufacture. Additionally, the latch mechanism can only be reset out of the double lock position by the electric motor. Thus if the vehicle's electric power fails while the latch assembly is double locked, even an authorized operator with the correct key will be locked out.
A second method for providing a double lock feature is described in U.S. Pat. No. 5,078,436 to Kleefeldt et al. As described therein, in the locked condition a coupling pin is moved to an uncoupled position. This uncouples an operating arm of the latch operating mechanism from an actuating lever which must be operated to unlatch the assembly. Double locking of the latch assembly is accomplished by an electric motor actuator having a motor whose output shaft is a spindle on which is threaded a nut that acts to move a two-part antitheft lever into a double lock position which blocks the coupling pin in the uncoupled position. If the vehicle's electric power fails, an outside key cylinder may be operated to move the blocking part of the antitheft lever into an unblocking position, allowing the latch assembly to be unblocked. However, only the electric motor actuator can move the two-part antitheft lever into the double lock position. Additionally, the assembly relies on a blocking action to keep the antitheft lever in the double lock position. Thus, again, the structure must be strong enough to to withstand whatever force a would-be thief is willing to apply. Hence, the elements must be made fairly robust and, therefore, are more expensive to manufacture.